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Re: Prelude conversion project - some questions

Posted: Sun, 18 Nov 2018, 21:17
by jonescg
The new jig spacer makes a much more convenient half-module assembly. The cordless driver with torque settings helps a lot too :)
Module assembly2.jpg
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Module assembly3.jpg
Module assembly3.jpg (197.76 KiB) Viewed 2274 times
I assembled another two enclosures this afternoon (^on the lower shelf of the workbench). I seem to have a system down now. With any luck I'll get the last one perfect :lol:

Re: Prelude conversion project - some questions

Posted: Mon, 19 Nov 2018, 04:58
by francisco.shi
How much does the brick weigh and how many kwh do you have per brick?

Re: Prelude conversion project - some questions

Posted: Mon, 19 Nov 2018, 06:31
by jonescg
The two row module weighs 18.6 kg and stores 3.2 kWh as a complete unit. So each brick of cells like the one above is about 9 kg.

Re: Prelude conversion project - some questions

Posted: Mon, 19 Nov 2018, 16:53
by tidalev
4Springs wrote:
Fri, 16 Nov 2018, 17:43

I used an off-the-shelf controller for this, mine uses a 0-5V signal (from memory) to control the speed based on the temperature of the coolant.
Do you have any more info on this? I'm looking at a similar setup

Re: Prelude conversion project - some questions

Posted: Mon, 19 Nov 2018, 18:51
by 4Springs
Controller info in this post.
viewtopic.php?f=18&t=5249#p64990
There are simpler controllers around if you just run the thing flat out.

Re: Prelude conversion project - some questions

Posted: Wed, 28 Nov 2018, 10:11
by jonescg
Not exactly a gigafactory, maybe a kilofactory?
3 modules worth.jpg
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Re: Prelude conversion project - some questions

Posted: Mon, 03 Dec 2018, 21:35
by jonescg
Managed to get a little help from Mike to bring the hoist up the hill. The Hyab truck they use to deliver and install wouldn't fit through the carport, so we had to unload it and roll it down to the shed. While we could have driven all the way back, we then wouldn't have a means to get it off the truck...

We can solve these minor issues :)
Hoist arrives.jpg
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Re: Prelude conversion project - some questions

Posted: Tue, 04 Dec 2018, 12:20
by Richo
I'm lost - what's that for

Re: Prelude conversion project - some questions

Posted: Tue, 04 Dec 2018, 12:29
by Johny
Richo wrote:
Tue, 04 Dec 2018, 12:20
I'm lost - what's that for
Looks to me like Chris is going to lower the car onto the battery pack😄
It's awfully big😱

Re: Prelude conversion project - some questions

Posted: Tue, 04 Dec 2018, 12:33
by jonescg
It's a car hoist. It will be installed in the workshop ahead of the Prelude conversion. Since the battery is going where the fuel tank used to be, the hoist will make the whole job a lot easier.

It's a clear-floor type, so they are taller than the regular 2-post hoists.

Re: Prelude conversion project - some questions

Posted: Wed, 05 Dec 2018, 12:33
by francisco.shi
Have you done any measurements on the cooling system for the battery pack?

Re: Prelude conversion project - some questions

Posted: Wed, 05 Dec 2018, 13:52
by jonescg
I've not yet set the modules up for testing, but I will have several tests to do by the weekend. The one module have already built is to be the 'spare' module, and it's just as well because the thermal epoxy doesn't have the sort of coverage I'd like it to have. It's probably 90 % as good as it needs to be.

However I found some Tesla pack data:
Tesla pack water temp graph.JPG
Tesla pack water temp graph.JPG (77.87 KiB) Viewed 2047 times
So this is a 1.2 C discharge on a Tesla Model S module. The measured internal resistance is about 100 mOhm per cell (remembering there are 74 in parallel and 6 of these in series - so the overall internal impedance of the pack is 0.0081 Ohm. At 297 amps it was generating 715 W of heat - for the first 30 seconds anyway. It dropped off as the voltage dropped.

The heat generation is plotted, as is the delta T in the coolant. From the delta T in the coolant we can infer the heat absorbed by the coolant.
Tesla pack water heat flux.JPG
Tesla pack water heat flux.JPG (70.94 KiB) Viewed 2047 times
It's rough, but should give some idea. Hope to have my data soon.

Re: Prelude conversion project - some questions

Posted: Wed, 05 Dec 2018, 16:10
by francisco.shi
Where did you get the data from. I would like to read a bit more about what other tests they did.

Re: Prelude conversion project - some questions

Posted: Thu, 06 Dec 2018, 09:26
by jonescg
I should add this was based on a measured DC IR of 100 mOhms per cell, which is probably higher than it really is. But not a lot higher. It's a used pack, so the DCIR has no doubt increased from new (which is supposed to be 60 mOhm).

Re: Prelude conversion project - some questions

Posted: Thu, 06 Dec 2018, 09:29
by jonescg
Potted my first complete battery pack with thermal epoxy. Next step is to wire up the BMS and test it :)
Potted pack.jpg
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Re: Prelude conversion project - some questions

Posted: Fri, 07 Dec 2018, 09:09
by jonescg
And then there were two.
2nd module done.jpg
2nd module done.jpg (141.05 KiB) Viewed 1985 times

Re: Prelude conversion project - some questions

Posted: Fri, 07 Dec 2018, 17:41
by mikedufty
Is that a zero motorcycle in the background?

Re: Prelude conversion project - some questions

Posted: Fri, 07 Dec 2018, 18:10
by jonescg
Yes, Daniel Klemm's bike. Still has problems and we're trying to re-flash the firmware to make it go. Currently a 50 km/h limited bike with 5 km range and won't take a charge... :(

Re: Prelude conversion project - some questions

Posted: Fri, 07 Dec 2018, 22:06
by mikedufty
Bummer

Re: Prelude conversion project - some questions

Posted: Sat, 08 Dec 2018, 21:02
by jonescg
I seem to have about a one-a-day sort of productivity right now.
Prelude modules.jpg
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And now there are four (and a spare).
4 done and a spare.jpg
4 done and a spare.jpg (220.67 KiB) Viewed 1881 times

Re: Prelude conversion project - some questions

Posted: Sun, 09 Dec 2018, 00:30
by rhills
Well, they look pretty professional IMHO.

How do you think those screws into perspex will hold up against vibration?

Re: Prelude conversion project - some questions

Posted: Sun, 09 Dec 2018, 06:55
by jonescg
It's polycarbonate which is tougher than perspex. The screws are also glued in place by virtue of the seal it goes through. I reckon they will be okay.

Re: Prelude conversion project - some questions

Posted: Sun, 09 Dec 2018, 08:34
by francisco.shi
Is the potting compound only on the bottom of the cells?

Re: Prelude conversion project - some questions

Posted: Sun, 09 Dec 2018, 11:02
by jonescg
francisco.shi wrote:
Sun, 09 Dec 2018, 08:34
Is the potting compound only on the bottom of the cells?
Correct. The bottom face of the cell stack represents about 20% of the total surface area, and it's all in the plane of the electrodes, so thermal conductivity is at it's highest.

Screenshot from a video I'm preparing:
potting screenshot.JPG
potting screenshot.JPG (129.06 KiB) Viewed 1875 times

Re: Prelude conversion project - some questions

Posted: Wed, 12 Dec 2018, 20:24
by jonescg
Almost ready to start work :D
Hoist installed.jpg
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